Thermoplastic fluoropolymer compositions

ABSTRACT

Thermoplastic fluoropolymer compositions, flexible, without whitening, comprising:  
     I) ETFE or ECTFE fluoropolymers modified with hydrogenated monomers;  
     II) one or more hydrogenated plasticizers;  
     III) one or more inorganic fire retardants;  
     IV) optionally other ingredients such as fillers, smoke retarders, intumescent agents, pigments, lubricants, organic fire retardants and thermal stabilizers.

[0001] The present invention relates to thermoplastic fluoropolymercompositions for the plenum wire insulation and cable jacketingapplications, that show a high time to ignition, a low smoke and heatrelease when put in contact with a heat source as for example in theCone Calorimeter (see the ASTM E1354 test).

[0002] More in particular the present invention relates to thermoplasticcompositions of fluoropolymers of ethylene with tetrafluoroethylene(ETFE) and/or chlorotrifluoroethylene (ECTFE), modified with one or morehydrogenated monomers.

[0003] The copolymers of ethylene and a fluorinated monomer such astetrafluoroethylene (TFE), chlorotrifluoroethylene (CTFE), or both, areknown in the art. It is also known the possibility to modify them withfluorinated unsaturated monomers in an amount between 0.1 and 10% bymoles. For example we mention the (per)fluoroalkylvinylethers in whichthe alkyl group has at least two carbon atoms, in particular theperfluoropropylvinylether (see U.S. Pat. No. 3,624,250). Other possiblecomonomers have the formula R′—CH═CH₂, where R′ is a perfluoroalkyl or aperfluoroalkoxy-perfluoroalkyl (see EP 185, 241, EP 185, 242)

[0004] The above mentioned ETFE and ECTFE copolymers non modified withfluoroolefins have poor affinity with hydrogenated substances, thesebeing polymers or high molecular weight compounds (for exampleplasticizers).

[0005] In EP 728,776 a special fluoroolefin able to copolymerize withfluorinated olefins giving for example a modified ETFE, is disclosed.This polymer shows good affinity with hydrogenated polymers, inparticular with aromatic polyesters.

[0006] In general the syntheses of special fluoroolefins are complex andtherefore they are used as comonomers in ethylene fluoropolymers onlywhen high performances are required. For example good chemicalresistance combined with excellent mechanical properties at hightemperatures (150°-200° C.).

[0007] The preparation of fluoropolymers blended with one or moreplasticizers to make the fluoropolymers flexible and usable in the cableindustry has a particular industrial interest. These polymers must becharacterized by the absence of the whitening phenomenon when the cableis bended.

[0008] The whitening effect must be avoided because it visuallyrepresents the plastic deformation of the material, and due to this itcannot recover the initial state. The electrical properties required forthis material are fully satisfied by the ECTFE which unfortunately has ahigh elastic modulus at room temperature, in general higher than 1500MPa and therefore it is not flexible.

[0009] In addition the ECTFE has a stress-strain curve at roomtemperature characterized by a necking at yield that makes it sensitiveto the whitening effect on the bended cable. The elastic modulus ofECTFE can be lowered by adding plasticizers, but in any case thematerial suffers of the whitening effect.

[0010] The Applicant, in order to overcome this problem, as disclosed inEP 866,079, has proposed the use of ETFE or ECTFE type fluoropolymersmodified with hydrogenated monomers blended with plasticizers, havinghigh flexibility and that do not show the whitening phenomenon.

[0011] However for safety reasons these flexible cables must show a hightime to ignition, a low smoke and heat release when put in contact witha heat source, as for example in the Cone Calorimeter (see the ASTME1354 test).

[0012] Unfortunately the presence of plasticizers increases the smokeand heat release.

[0013] The Applicant has found that when using fire retardants in thepolymers compounded with plasticizers, it is possible to obtain flexiblecompositions having the following combination of properties:

[0014] good mechanical properties,

[0015] absence of the whitening effect,

[0016] decrease of smoke and heat release when tested in a ConeCalorimeter according to the ASTM E1354 test.

[0017] An object of the present invention is a composition comprising:

[0018] I) ETFE or ECTFE fluoropolymers modified with hydrogenatedmonomers;

[0019] II) one or more hydrogenated plasticizers;

[0020] III) one or more inorganic fire retardants;

[0021] IV) optionally other ingredients such as fillers, smokeretarders, intumescent agents, pigments, lubricants, organic fireretardants and thermal stabilizers.

[0022] More in particular the component I) of the compositions of theinvention is a copolymer formed of:

[0023] (a) from 10 to 70%, preferably from 35 to 55%, by moles ofethylene,

[0024] (b) from 30 to 90%, preferably from 45 to 65%, by moles of afluorinated monomer selected from tetrafluoroethylene,chlorotrifluoroethylene, or mixtures thereof,

[0025] (c) from 0.1 to 30%, preferably from 1 to 15%, by moles of ahydrogenated monomer of formula:

CH₂═CH—(CH₂)_(n)—R₁  (I)

[0026] where R₁=—OR₂, —(O)_(t)CO(O)_(p)R₂ wherein t and p are integersequal to 0 or 1 and R₂ is a hydrogenated radical from 1 to 20 carbonatoms, C₁-C₂₀, linear and/or branched alkyl radical, or cycloalkylicradical, or R₂ is H. The R₂ radical can optionally contain: heteroatomspreferably O, N; halogens preferably Cl; one or more functional groups,preferably selected from OH, COOH, epoxide, ester and ether; and doublebonds. The above mentioned n is an integer in the range 0-10.

[0027] Preferably R₂ is an alkyl radical from 1 to 10 carbon atomsoptionally containing one or more hydroxy functional groups, n is aninteger in the range 0-5.

[0028] The preferred comonomers (c) are for example selected from thefollowing classes:

[0029] 1) Acrylic monomers of formula:

CH₂═CH—CO—O—R₂

[0030] wherein R₂ has the aforesaid meaning.

[0031] For example ethylacrylate, n-butylacrylate, acrylic acid,hydroxyethylacrylate, hydroxypropylacrylate,(hydroxy)ethylhexylacrylate, etc., can be mentioned.

[0032] 2) Vinylether monomers of formula:

CH₂═CH—O—R₂

[0033] wherein R₂ has the aforesaid meaning.

[0034] For example propylvinylether, cyclohexylvinylether,vinyl-4-hydroxybutylether, etc., can be mentioned.

[0035] 3) Vinyl monomers of the carboxylic acid of formula:

CH₂═CH—O—CO—R₂

[0036] wherein R₂ has the aforesaid meaning.

[0037] For example vinyl-acetate, vinylpropionate,vinyl-2-ethylhexanoate, etc., can be mentioned.

[0038] 4) Unsaturated carboxylic acid of formula:

CH₂═CH—(CH₂)_(n)—COOH

[0039] wherein n has the aforesaid meaning. For instance vinylaceticacid, etc.

[0040] The most preferred monomer of formula (I) is n-butyl acrylate.

[0041] Components II) are hydrogenated plasticizers well known in theart and used in the hydrogenated (co)polymers, from 1 to 20% by weight,preferably from 5 to 10% by weight referred to the total weight of thecomposition.

[0042] Examples of plasticizers, not limitative for the presentinvention, are: 2-ethylhexyldiphenylphosphate, neopentylglycoldibenzoate, tricresylphosphate, tetrabromophtalate ester,tri-n-hexyl-trimellitate, ethylene glycol monostearate,acetyltri-n-hexyl citrate; preferably acetyltri-n-butyl citrate(Citroflex® A4), tributyl trimellitate and tri-n-hexyltrimellitate.

[0043] Components III) are the inorganic fire retardants used in amountsfrom 0.2 to 35% by weight, preferably from 1 to 15% by weight, referredto the total weight of the composition.

[0044] The fire retardants are well known in the art of hydrogenated(co)polymers. We can mention for example: inorganic phosphates (forexample, ammonium phosphate), metal oxides (for example, aluminum oxide,aluminum oxide trihydrate, antimony oxides, molybdenum oxide), tinoxalates, boron compounds (for example, borax, zinc borate, Firebrake®ZB), metal hydroxide (for example, magnesium hydroxide, or hydroxidemixture such as Zn(OH)₂ and Sn(OH)₄ e.g. ZnSn(OH)₆).

[0045] Components IV) are used in amounts from 0.1 to 15% by weight,preferably from 0.5 to 5% by weight, referred to the total weight of thecomposition.

[0046] The optional ingredients are fillers (for example,polytetrafluoroethylene (PTFE), silicates, mica, metal oxide coatedmica, mica blended with metal oxides), smoke retarders, lubricants,pigments, organic fire retardants (for example, halogenated compounds aschloroparaffins, brominated polyesters, brominated epoxy oligomers);intumescent agents and thermal stabilizers as, for example, Irganox®1010.

[0047] Furthermore the Applicant has surprisingly found that the use ofinorganic fire retardants treated with dispersing agents with respect tothe simple addition of inorganic fire retardants to the plasticized ETFEor ECTFE fluoropolymer type modified with hydrogenated monomers, leadsto a further unexpected increase of the time to ignition and to afurther substantial decrease of smoke and heat release according to theASTM E1354 test run in a Cone Calorimeter.

[0048] Therefore a further object of the present invention is the use ofinorganic fire retardants treated with dispersing agents as hereinafterdescribed.

[0049] The inorganic fire retardants are treated with dispersing agentsin amounts ranging from 0.01 to 10% by weight, more preferably from 0.1to 5% by weight.

[0050] Optionally, the inorganic components IV) of the composition canbe treated with dispersing agents in an amount ranging from 0.01 to 10%by weight, more preferably from 0.1 to 5% by weight. For example fillers(e.g. mica) treated together with the fire retardants or singly withdispersing agents.

[0051] The dispersing agents according to the present invention arethose known in the art to disperse fillers and that satisfy one of thefollowing tests:

[0052] Test 1: any substance able to disperse inorganic fillers likesilica, for example cristobalite, having at least 95% of the particleswith average diameter of 2 μm, in solvents like methyl methacrylate. Adispersion is a system in which the particles of the filler aredispersed in the solvent or easily redispersable after segregation;

[0053] Test 2: any substance able to homogeneously disperse theinorganic fire retardants and/or the inorganic components IV) in anothersolid phase of known particle size distribution. The degree ofdispersion, can be estimated by a visual analysis of a tablet of thedispersion using a coloured solid matrix.

[0054] The preferred dispersing agents according to the presentinvention have formula:

(R₃)_(4-m)A(X)_(m)  (II)

[0055] wherein m is an integer from 1 to 3, A is Si or Ti or Zr and X isa hydrolyzable group, R₃ is an oligomer of hydrogenated monomers or aC₁-C₁₅ alkyl and/or aryl radical. The R₃ radical can contain:unsaturations; one or more heteroatoms selected from: O, N, S, orhalogens such as Cl; functional groups such as amine, epoxide, thiogroup —SH, hydroxide, carboxyl and carboxylate.

[0056] Among these, the preferred dispersing agents, in a monomeric oroligomeric form, are those wherein m is 2 or 3; X is a hydrolyzablegroup where X is preferably an alkoxy group OR₄ in which R₄ is a C₁-C₅linear or branched alkyl radical, preferably R₄ is methyl or ethyl; R₃and A are as above defined. Preferably A is Si and/or Ti. When A isequal to Si preferably m=3 and R₄ is methyl or ethyl.

[0057] For example we can mention: vinyltriethoxysilane,3-aminopropyltriethoxysilane, 3-chloroisobutyltriethoxysilane,3-mercaptopropyltriethoxysilane, octyltriethoxysilane,bisacetylacetonate diisopropoxytitanate.

[0058] As examples of oligomeric form of dispersing agents according tothe formula (II) we can mention those of silane A-174. In the case R₃ isformed by hydrogenated monomers, we can mention, for example, theacrylic acid esters.

[0059] The addition of the dispersing agents to the inorganic fireretardants and to the inorganic component IV) is preferably carried outat room temperature and followed by a thermal treatment at about 100° C.for one or more hours. The water required for the hydrolysis of thedispersing agents comes from the reaction medium and/or from thesolution containing one or more dispersing agents, or from theenvironment.

[0060] The following examples are given for illustrative purposes butare not limitative of the present invention.

[0061] In Table 1 the tests have been carried out according to the ASTME1354 method for the time to ignition; heat and visible smoke releaserates for materials and products using an Oxygen ConsumptionCalorimeter; Radiant Heat Flux 90 Kw/m²; sample weight 50 g; horizontalsample direction.

EXAMPLE 1

[0062] In an enamelled autoclave equipped with baffles and stirrerworking at 450 rpm in Hastelloy C, 7 l of demineralized water, 15.5 g ofchloroform, 10 g of n-butylacrylate and 2 kg of chlorotrifluoroethylenewere introduced. The temperature reaction was set and maintained at 15°C. Then ethylene was charged up to a pressure of 8.2 absolute bars. Inthe autoclave the radical initiator was then continuously introducedduring the whole polymerization time, under the form of a solution,maintained at −17° C., of trichloroacetyl-peroxide (TCAP) in isooctanewith titre of 0.1 g TCAP/ml. In addition 10 g of n-butylacrylate werecharged to the reactor at consumption of 20, 40, 60, 80, 100, 120, 140,160 and 180 g of ethylene.

[0063] The pressure was maintained constant for the whole polymerizationby continuously feeding ethylene in the reactor up to a consumption of200 g; the total amount of initiator solution was of 210 ml. Thepolymerization lasted 405 minutes.

[0064] Then the polymer produced was dried at 120° C. for about 16hours. The total dry weight was of 1530 g.

[0065] The polymer was then compounded with MARK-260® 0.45% by weightand Aclyn-316® 0.15% by weight both mainly used as thermal stabilizers.

[0066] Some characteristics of this polymer (defined Polymer A) are thefollowing: the Melt Flow Index (M.I.) according to ASTM 3275-89 methodis of 9 g/10′; the second melting point (T_(mII)) determined byDifferential Scanning Calorimetry (DSC) is 190° C. and the molarcomposition obtained by carbon elemental analysis and by materialbalance is ethylene 40% by moles, chlorotrifluoroethylene 55% by molesand n-butylacrylate 5% by moles.

EXAMPLE 2 (COMPARATIVE)

[0067] The polymer powder A has been blended with Citroflex® A4 in anamount equal to 7% by weight based on the blend. Then the blend has beenpelletized in a twin-screw extruder. This compound has been tested in aCone Calorimeter according to the ASTM E1354 method. Table 1 reportstime to ignition, peak heat release rate, total heat released andaverage extinction coefficient related to the smoke for a sample of 50 gby weight.

EXAMPLE 3

[0068] The polymer powder A blended with Citroflex® A4 as in Example 2has been compounded with zinc borate (Firebrake® ZB 500) 5% by weightand mica 1% by weight based on the total weight. Then the blend has beenpelletized in a twin-screw extruder. This compound has been tested in aCone Calorimeter according to the ASTM E1354 method. Table 1 reportstime to ignition, peak heat release rate, total heat released andaverage extinction coefficient related to the smoke for a sample of 50 gby weight.

EXAMPLE 4

[0069] As in Example 3 except that zinc borate and mica are blended with2% by weight of water-borne-3-aminopropyl-triethoxysilane, and thenthermally treatment at 100° C. for two hours. Then the blend has beenpelletized in a twin-screw extruder. This compound has been tested in aCone Calorimeter according to the ASTM E1354 method. Table 1 reportstime to ignition, peak heat release rate, total heat released andaverage extinction coefficient related to the smoke for a sample of 50 gby weight.

EXAMPLE 5

[0070] As in Example 3 except that zinc borate and mica are blended with2% by weight of a solution formed by 75% by weight of bisacetylacetonatediisopropoxytitanate and 25% by weight of isopropanol, and thenthermally treated at 100° C. for two hours. Then the blend has beenpelletized in a twin-screw extruder. This compound was tested in a ConeCalorimeter according to the ASTM E1354 method. Table 1 reports time toignition, peak heat release rate, total heat released and averageextinction coefficient related to the smoke for a sample of 50 g byweight.

[0071] The mechanical properties at 23° C. according to the ASTM D1708test of compression moulded specimen of the compound are shown in Table2.

EXAMPLE 6

[0072] As in Example 3, except that zinc borate and mica are blendedwith 2% by weight of a solution formed by 75% by weight ofbisacetylacetonate diisopropoxytitanate and 25% by weight of isopropanoland with 2% by weight of water-borne 3-aminopropyltriethyoxysilane, andthen thermally treated at 100° C. for two hours. Furthermore, 1% byweight of PTFE (POLYMIST®) has been added to the compound and thenpelletized in a twin-screw extruder.

[0073] This compound has been tested in a Cone Calorimeter according tothe ASTM E1354 method. Table 1 reports time to ignition, peak heatrelease rate, total heat released and average extinction coefficientrelated to the smoke for a sample of 50 g by weight.

[0074] The mechanical properties at 23° C. according to the ASTM D1708test of compression moulded specimen of the compound are shown in Table2.

[0075] From Tables 1 and 2 it can be observed that the compositions ofthe invention are characterized by having good mechanical properties,they are flexible, they do not show the whitening effect and they haveexcellent flame-retardant and smoke-suppressed properties. TABLE 1 ConeCalorimeter data according to the ASTM E1354 method. Radiant Heat Flux90 Kw/m². Horizontal orientation of the sample. Average extinction Timeto Peak heat Total heat coefficient ignition release rate released(smoke) Examples sec. Kw/m² MJ/m² m²/g Example 2 (comp)  16 203 25,30,631 Polymer A (P) Example 3  15 141,6 24,3 0,525 Polymer A (P,FR)Example 4 210 41,3 12,4 0,139 Polymer A (P,SiFR) Example 5 220 40,7 12,90,124 Polymer A (P,TiFR) Example 6 196 32,6 12,8 0,114 Polymer A(P,L,SiTiFR)

[0076] TABLE 2 Mechanical Example 5 Example 6 properties Polymer APolymer A 23° C. (P,TiFR) (P,L,SiTiFR) Elastic 270 280 modulus (MPa)Stress  10  10 at yield (MPa) Elongation (*) (*) at yield (%) Stress  27 28 at break (MPa) Elongation 260 270 at break (%)

1. Thermoplastic fluoropolymer compositions, flexible without whitening, comprising: I) ETFE or ECTFE fluoropolymers modified with hydrogenated monomers; II) one or more hydrogenated plasticizers; III) one or more inorganic fire retardants; IV) optionally other ingredients such as fillers, smoke retarders, intumescent agents, pigments, lubricants, organic fire retardants and thermal stabilizers.
 2. Compositions according to claim 1 wherein the component I) is a copolymer formed of: (a) from 10 to 70%, preferably from 35 to 55%, by moles of ethylene, (b) from 30 to 90%, preferably from 45 to 65%, by moles of a fluorinated monomer selected from tetrafluoroethylene, chlorotrifluoroethylene, or mixtures thereof, (c) from 0.1 to 30%, preferably from 1 to 15%, by moles of a hydrogenated monomer of formula: CH₂═CH—(CH₂)_(n)—R₁  (I) where R₁=—OR₂, —(O)_(t)CO(O)_(p)R₂ wherein t and p are integers equal to 0 or 1 and R₂ is a hydrogenated radical from 1 to 20 carbon atoms, C₁-C₂₀, linear and/or branched alkyl radical or cyclo-alkyl radical or R₂ is H; the R₂ radical may optionally contain: heteroatoms preferably O, N or a halogen preferably Cl; one or more functional groups preferably selected from OH, COOH, epoxide, ester and ether; and double bonds; the above mentioned n is an integer in the range 0-10; preferably R₂ is an alkyl radical from 1 to 10 carbon atoms containing one or more hydroxy functional groups and n is an integer in the range 0-5; the components II) are well known hydrogenated plasticizers used in the hydrogenated (co)polymers, from 1 to 20% by weight, preferably from 5 to 10% by weight; the components III) are the inorganic fire retardants from 0.2 to 35% by weight, preferably from 1 to 15% by weight; the components IV) are ingredients from 0.1 to 15% by weight, preferably from 0.5 to 5% by weight.
 3. Compositions according to claim 2 wherein the comonomers (c) of the component I) are selected from: 1) acrylic monomers having the formula: CH₂═CH—CO—O—R₂ wherein R₂ has the aforesaid meaning; 2) vinylether monomers having the formula: CH₂═CH—O—R₂ wherein R₂ has the aforesaid meaning; 3) vinyl monomers of the carboxylic acid of formula: CH₂═CH—O—CO—R₂ wherein R₂ has the aforesaid meaning; 4) unsaturated carboxylic acids of formula: CH₂═CH—(CH₂)_(n)—COOH wherein n has the aforesaid meaning.
 4. Compositions according to claims 2-3 wherein the comonomers (c) of the component I) are selected from: ethylacrilate, n-butylacrilate, acrylic acid, hydroxyethylacrylate, hydroxypropylacrylate, (hydroxy)ethylhexylacrylate; propylvinylether, cyclohexylvinylether, vinyl-4-hydroxybutylether; vinylacetate, vinylpropionate, vinyl-2-ethylhexanoate; vinylacetic acid.
 5. Compositions according to claims 2-4, wherein the preferred monomer of formula (I) is n-butyl acrylate.
 6. Compositions according to claims 1-5 wherein the component II), the hydrogenated plasticizers, are selected from: 2-ethylhexyldiphenylphosphate, neopentyl glycoldibenzoate, tricresylphosphate, tetrabromophthalic ester, tri n-hexyl-trimellitate, ethylene glycol monostearate, acetyl tri-n-hexyl citrate; preferably acetyl tri-n-butyl citrate, tributyl trimellitate and tri-n-hexyltrimellitate.
 7. Composition according to claims 1-6, wherein the component III), the inorganic fire retardants, are selected from: inorganic phosphates (ammonium phosphate), metal oxides (aluminum oxide, aluminum oxide tri-hydrate, antimonium oxides, molybdenum oxide), tin oxalates, boron compounds (borax, zinc borate, Firebrake® ZB), metal hydroxide (magnesium hydroxide, or hydroxide mixture preferably Zn(OH)₂ and Sn(OH)₄).
 8. Compositions according to claims 1-7 wherein the component IV) are polytetrafluoroethylene (PTFE), mica, metal oxide coated mica and mica blended with metal oxides or mixture thereof.
 9. Compositions according to claims 7-8 wherein the inorganic fire retardants are treated with dispersing agents in amounts ranging from 0.01 to 10% by weight, more preferably from 0.1 to 5% by weight.
 10. Compositions according to claims 6-9 wherein one or more of the inorganic compounds of the component IV) are treated with dispersing agents in amount ranging from 0.01 to 10% by weight, more preferably from 0.1 to 5% by weight.
 11. Compositions according to claims 9-10 wherein the dispersing agents have formula: (R₃)_(4-m)A(X)_(m)  (II)wherein m is an integer from 1 to 3, A is Si or Ti or Zr and X is an hydrolyzable group, R₃ is an oligomer of hydrogenated monomers or C₁-C₁₅ alkyl and/or aryl radical; the R₃ radical optionally containing: unsaturations; one or more heteroatoms selected from: O, N, S, or halogen such as Cl; functional groups like amine, epoxide, thio group (—SH), hydroxide, carboxyl and carboxylate.
 12. Compositions according to claim 11 , wherein the dispersing agents, in a monomeric or oligomeric form, have m=2 or 3; X is a hydrolyzable group, preferably x is an alkoxy group OR₄ in which R₄ is a C₁-C₅ linear or branched alkyl radical; preferably A is Si and/or Ti; when A is equal to Si preferably m=3 and R₄ is methyl or ethyl.
 13. Compositions according to claims 11-12 wherein the dispersing agents are selected from: vinyltriethoxysilane, 3-aminopropyltriethoxysilane, 3-chloroisobutyltriethoxysilane, 3-mercaptopropyltriethoxysilane, octyltriethoxysilane, bisacetylacetonate diisopropoxytitanate.
 14. Compositions according to claims 9-13 wherein the addition of the dispersing agent to the inorganic fire retardants and/or to one or more inorganic compounds of the component IV) is preferably carried out at room temperature and then thermally treated at about 100° C. for one or more hours, the water required for the hydrolysis of the dispersing agents comes from the reaction medium and/or from the solution containing the dispersing agents, or from the environment. 